1. Field of the Invention
The present invention relates to a travel system for a hybrid type motor vehicle.
2. Description of the Prior Art
Hybrid type motor vehicles combine, as a traction or propulsion drive means, a thermal engine which is generally an internal-combustion engine, and a rotary electric machine connected to an electric source, such as one or more electric accumulators. This combination allows the performance of the vehicle to be optimized, notably by limiting the discharge of pollutants to the atmosphere and by decreasing the fuel consumption of the entire device.
As it is already known, notably from French Patent Application No. 2,670,440, hybrid vehicles comprise a drive system with a thermal engine including an output shaft connected to a speed variation device and an electric machine connected to an electric battery. This system also comprises two clutches with a first clutch between the thermal engine and the electric machine and a second clutch between the electric machine and the speed variation device.
Thus, when the vehicle is to be driven with a high torque available over a wide speed range while limiting exhaust gas and noise generation, as in an urban site, the electric machine is preferably used for driving the motive axle of the vehicle.
On the other hand, for uses where a high driving power and a wide operating range are required, the thermal engine is used for driving the motive axle and thus providing powering of the vehicle.
Although satisfactory, this drive system however involves some significant drawbacks.
In fact, when only the electric machine is used to drive the vehicle, sufficient torque is required therefrom for driving the vehicle as well as overcoming all the resistances (inertia, friction, . . . ) inherent in the vehicle and in the speed variation device.
Furthermore, during vehicle braking, part of the energy released thereby is absorbed by the speed variation device and only a minor part of this energy is recovered which is then converted to electric power by the electric machine.